The present disclosure relates to energy generation and more specifically to multiphase generator-conversion systems.
Modern wind turbines are commonly used to supply electricity into the electrical grid. Although the electrical grid is typically an AC grid, some applications exist for which DC technologies may be used. That may be the case of offshore wind power plants, where DC wind turbine power plants may be used instead of AC wind turbine power plants if they have to be connected to a high-voltage, direct current (HVDC) link. DC wind turbine power plants are wind turbine power plants with an internal DC collection grid, instead of a conventional AC collection grid.
Typically, some wind turbines employ permanent magnet generators. One type of permanent magnet generators are multiphase AC generators with n i-phase stators (typically 3-phase stators). In order to implement DC wind power plants using conventional multiphase AC wind turbine generators, the output of the wind turbine's power conversion system must be in DC. Therefore, n×i-phase (typically 3-phase) permanent magnet generators of wind turbines need to be adjusted for their usage in a DC collection grid. Since the output voltage must be in DC and the permanent magnet generators are in AC, AC/DC converters are required to carry out the conversion. This conversion may imply a large number of power converters and the necessity of large power transformers. The large amount of components required is not desirable due to space and weight restrictions of wind turbines, even more so in offshore configurations where transportation, maintenance and servicing raises the overall cost of the installation.
The present disclosure relates to various methods and devices for avoiding or at least partly reducing this problem.